Fabrication of Soft Magnetic Fe-Ni Films by Direct Deposition of Nanoparticle Agglomerates Using Cold-Spray Technique

The development of advanced soft magnetic devices requires high-performance soft magnetic materials and a high degree of design freedom. Fe-based nanoparticles are attracting attention as high-performance soft magnetic materials. When using nanoparticles as a starting material, achieving high packing density without changing their particle size remains a challenge. Nanoparticle films with high particle density consisting of Fe-Ni soft magnetic nanoparticles were fabricated by direct deposition using the cold-spray technique. The packing density of the particles was estimated to be greater than 78%, which is 20% larger than that of conventional compression-molded products at room temperature. The size of the Fe-Ni nanoparticles in the film was maintained, and no grain growth was observed after cold spraying. The magnetic permeability of the nanoparticle films was higher than that of the compression-molded products because of the larger packing density of the particles. These results indicate that the cold-spray technique is suitable for the fabrication of bulk-like structures using nanoparticle materials.